In May, the U.S. Supreme Court struck down the Professional and Amateur Sports Protection Act of 1992, a federal statute that limited regulated sports betting to primarily Nevada for 26 years.

Since the ruling, four additional states -- Delaware, Mississippi, New Jersey and West Virginia -- have started taking bets, with Pennsylvania and Rhode Island expected to be among the next wave of states to open sportsbooks. Within a few years, experts believe more than 25 states will be offering legal betting, including online options in some jurisdictions.

The U.S. is in early stages of building what many believe will be the largest legal sports betting market in the world, potentially generating hundreds of billions of dollars in bets once fully mature. But not everyone is excited.

Problem gamblers, the services that attempt to help them, and opposition groups worried about any societal scourge that might result from expanded legal sports betting are concerned that their voices are being drowned out as more states open sportsbooks.